Lapping machine tool



May 28, 1968 R. s. GENTRY ET AL 3,385,008

LAPPING MACHINE TOOL Filed Feb. 25, 1966 4 Sheets-Sheet 1 w z I .8

l l'lllll l l llll IW I06 I O 96 2 INVENTORS Richard S. Gentry Fig. 1 Geme A. Sowden B WLM TO R NEYS May 28, 1968 R. s. GENTRY ET AL 3,385,008

LAPPING MACHINE TOOL Filed Feb. 25, 1966 4 Sheets-Sheet 3 I 32 5 I 48 4ev 1 \20 {Mo 2 I V INVENTORS Rwhard S. Genfirg F1 4- TTORNEYS y 8, 1968R. s. GENTRY ET AL 3,385,008

LAPPING MACHINE TOOL 4 Sheets-Sheet 4.

Filed Feb. 25, 1966 I 4 GM W M T C J M 2 CL M H H I 3 W slmfw Rnnw 0 5T6 N S a Enao u A R N a o T T mm m owe O/ G United States Patent3,385,008 LAPPING MACHINE TOOL Richard S. Gentry and George A. Sowden,Indianapolis, Ind., assignors, by mesne assignments, to Richard S.Gentry, Indianapolis, Ind.

Filed Feb. 25, 1966, Ser. No. 530,105 Claims. (Cl. 51--34) ABSTRACT OFTHE DISCLOSURE An improved lapping machine tool. A lapping tool isbiased forward by an air cylinder and is reciprocated by a cam whichretracts the tool against the bias and controls the rate of its advanceunder the limited bias force. Work piece resistance arrests the tool atan intermediate point in its forward strokes, and as the lappingprogresses to overcome such resistance, the tool advance beyond sucharrest point actuates a switch to energize a feed motor which advancesthe stroke range. Such switch is adjustable to adjust the Operatingstroke length. The tool reciprocating mechanism is mounted on a headabove the work piece table. The feed motor is housed in the base and isan air cylinder which operates through adjustable strokes to actuate afeed screw to lower the head. An electrical motor operates the feedscrew for rapid feed.

This invention relates to a machine tool for automatically performinglapping and like abrading and metal finishing operations.

It is a principal object of the invention to provide an improved machinetool embodying the general concept of that shown in United States PatentNo. 3,151,992. In that patent, a lapping tool is biased forward by alimited resilient force, such as that of a spring or an air cylinder,and is reciprocated through a predetermined stroke range by a cam whichacts to drive it in a retraction direction against such bias and tocontrol the rate of its advance movement by the biasing force; so thatthe forward stroke of the tool is under a limited force sufiicient toproduce the desired lapping but insufficient to produce galling. Inoperation, the tool is arrested at an intermediate point in its forwardstrokes by the workpiece resistance, and as the lapping progresses toovercome such resistance and the tool advances beyond such arrest pointin a forward stroke, such movement actuates a switch to energize a feedmotor which advances the stroke range.

It is a further object of the present invention to provide a machine forcarrying out such lapping operations, which will be practical for a widevariety of lapping work and will provide a high degree of accuracy, andwhich will have improved controls and regulations.

In the preferred form of the present invention, the lapreciprocat-ingmechanism is mounted in a head assembly positioned above a work tableand rigidly carried by slidable posts accurately guided forperpendicular movement through the plane of the table and connected attheir lower ends to a vertically movable platen. The platen is raisedand lowered by a main feed screw, which may be a non-rotating screwengaged in an internally threaded output gear of a reduction gear set,such as a worm and worm-wheel set. The gear set is connected foroperation either by an electric motor, for rapid feed, or by anadjusta'ble-stroke incremental feed device, such as an airdriven rackand pinion.

The lap-reciprocating mechanism is driven by a variable-speed motor andthe lap carrier is biased toward the work by an air cylinder, and boththe rate and force of lapping strokes are accurately adjustable over awide "ice range. The incremental feed device is actuated through asingle stroke of adjustable length in response to movement of the lapcarrier, in each lap stroke, beyond an intermediate point of the strokerange, and adjustment is provided both of the position of suchintermediate point and of the length of the feed increment produced.Accordingly, accurate regulation and adjustment of all lappingconditions is provided.

The accompanying drawings illustrate the invention. In such drawings:

FIG. 1 is a front elevation of a machine embodying the invention, withparts broken away to show the operating mechanism;

FIG. 2 is a vertical section of the machine of FIG. 1, taken on the line2-2 of FIG. 1;

FIG. 3 is a horizontal section, taken on the line 3-3 of FIG. 1, showingthe head mechanism in plan;

FIG. 4 is a horizontal section, taken on the line 44 of FIG. 1, showingthe feed mechanism in plan; and

FIG. 5 is an electrical diagram of the operating and control devices ofthe machine of FIG. 1.

The machine shown in the drawings comprises a base 10 formed of a rigidframe enclosed in a housing and supporting a work table 12 in ahorizontal plane. Vertical guide bearings 14 at the four corners of thetable 12 slidably receive guide posts 16 which are interconnected attheir lower ends by a platen 18 and which rigidly support a head 20above the table 12. The head 20 is adapted to be raised and lowered withrespect to the table 12 by feed mechanism housed in the base 10, asdescribed below.

The head 20 comprises a frame 22 which forms a central housing 24 for abushing 26 in which a vertically reciprocable shaft or lap carrier 28 ismounted. Above the housing 24, the frame supports a pair of side plates30 provided with bearings 32 in which a horizontal cam shaft 34 ismounted. The shaft 34 carries a central eccentric cam 36, and this isembraced by a yoke 38 having a cam-follower insert 40 bearing downwardlyagainst the cam 36. The lower end of the yoke 38 is connected to the lapcarrier 28, and the upper end of the yoke 38 is engaged for downwardthrust by the piston rod 42 of an air cylinder 44. As is shown in FIG.1, the yoke 38 has a lateral extension 46 which carries a guide bearing48 received over a fixed guide pin 50, for the purpose of guiding theyoke for vertical movement and against lateral thrust from the cam 36.

The eccentric cam 36 may desirably have a throw or eccentricity of of aninch, so that it provides a reciprocating stroke range for the lapcarrier 28 of of an inch. The shaft 34 carries a large pulley 52, bywhich it is belt driven from a smaller pulley 54 on the shaft of avariable-speed electric motor 56. Desirably, the reciprocation rate ofthe lap carrier 28' is variable from O to 600 strokes per minute. Theair cylinder 44 is suppled with air pressure from any suitable source,controlled by a manually adjustable valve 58, and the pressure isdesirably shown on an air gauge 60. The downward thrust exerted by theair cylinder 44 on the yoke 38 and hence on the lap carrier 28 isdesirably variable to produce lapping pressures of from 0 to 400 pounds.

The lower end of the lap carrier 28 has an internally threaded bore inwhich is fitted a lap holder 62 by which a lap 64 is rigidly secured tothe lap carrier 28.

The workpiece 66 to be lapped is mounted on blocks 68 on the table 12and secured in place by suitable holddown clamps 70.

As shown in FIGS. 1 and 3, the lateral extension 46 on the yoke 38carries a vertically adjustable screw 72 having a switch actuating head74 at its lower end disposed to engage a feed switch S1 at anintermediate point in the downward reciprocating stroke of the yoke 38and its lap carrier 28. This is the feed actuating switch, the functionof which will be described below. The frame of the head 20 also carriesa limit switch S-5 having an actuating arm positioned to be engaged byan adjustable rod 78 fixed to the table 12. This serves to terminate thelapping operation when downward feed movement of the head is sufficientto show that the lapping operation has been completed.

As is shown in FIGS. 1 and ,2, the platen 18 which carries the lowerends of the head supporting posts 16 is arranged to be raised andlowered by feed mechanism in the base 10. To this end, the platen 18-rests on a plate 80 carried by a feed screw 82 which extends downwardthrough a reduction gear set 84 by containing a worm wheel (not shown)threaded onto and forming a runner on the feed screw 82 and driven by aworm on a cross shaft 86. The plate 80 is fixed to the feed screw 82 andis held against rotation by a pair of bolts 88 screwed into the platen18 but sufliciently long to allow the plate 80 to retract away from theplaten 18- with lost motion, in the event the head does not follow thelowering action of the feed screw 82.

As shown in FIG. 1, the feed screw plate 80 carries a switch-actuatingcam 90 which, in the event of such lost motion retraction, will actuatea limit switch S-4 to interrupt downward feed. A limit switch S2 ismounted on the base in position to be actuated by the platen 18 tointerrupt upward feed at a suitable limit point.

In the feed mechanism, as shown in FIG. 2, the right end of the inputshaft 86 of the gear set 84 is connected through an electromagneticbrake 92 to a pulley 94 which is belt driven from a reversible motor 96.This provides for manual raising and lowering of the platen 18 and head20.

The opposite or left end of the input shaft 86 is connected through anelectromagnetic clutch 102 to a pinion gear 104 engaged by a rack 106connected to be reciprocated by an air cylinder 108 shown in FIGS. 1 and4. The air cylinder 108 is connected to a suitable source of air underpressure through a solenoid valve 110 operated by a solenoid 112. In thenormal position of the solenoid valve 110, as shown in FIG. 4, itsupplies air to the cylinder 108 to bias its piston to the left to holdthe rack in the leftward position shown in FIGS. 1 and 4. When thesolenoid 112 is actuated, it supplies air to the cylinder 108 to drivethe piston and the rack 106 to the right against an adjustable stop 114.

In the leftward position of the rack 106, a switch actuator arm 116 onthe rack moves a switch S-6 to an actuated position with its maincontacts S-6a open and with its timer contacts S-6b closed. When therack 106 moves to the right against the stop 114, a switch-actuating arm118 engages a reversing switch 5-3 which has the effect of deenergizingthe solenoid to cause the rack 106 to be driven to the left by the aircylinder 108.

Controls for the machine may be mounted in the housing of the base asshown in FIG. 1, and include manual UP and DOWN switches 120 and 122, areset button 124, a manual Run/Stop switch 126, a Hand/Auto switch 128for setting the machine for either hand or automatic operation, and atimer 132 to interrupt operation if the lapping process does not proceedat a suitable rate. A stroke-rate control potentiometer 156 for varyingthe speed of the head motor 56 is also included in the control grouping.

The electrical supply and control system may be as shown in FIG. 5. Theplaten feed motor 96 is connected to a three-wire 2,20 v. supply line140 through a reversing contactor 142 having UP and DOWN actuating coils143 and 144. A transformer 146 supplies 110 v. current to a two-wirecircuit having a grounded wire 150 and a live wire 152.

A controller-rectifier unit 154 connected to the circuit 150-152provides power to the head motor 56, and a potentiometer 156 controlsthe motor speed. A control circuit 158 for the unit 154 stops the motor56 when closed. Such control circuit contains the manual Run/ Stopswitch 126; and contains contacts 128a of the Hand/Auto switch 128 inseries with the normally open contacts S-Sa of the limit switch S-5 andwith a parallel timer switch 134.

A converter 160 connected across the circuit 150-152 provides DC.current for the windings of the brake 92 and clutch 102.

The Hand/Auto switch 128 comprises the contacts 128a which close torender the limit switch contacts S-Sa and timer switch 134 effective forautomatic operation; contacts 128b which bridge the interlock relay R-3during hand operation; selector contacts 128a for the brake circuit,selector contacts 128d for the clutch 102 circuit, selector contacts128:; for energizing the manual controls for the platen motor 96; andselector contacts 128 for energizing the automatic controls.

The manual UP switch comprises normally-closed contacts 120a in thebrake circuit and normally-open contacts 120b to energize the UP coil143 of the contactor 142. The DOWN switch 122 comprises normallyclosedcontacts 122a in the brake circuit and normallyopen contacts 12211 toenergize the DOWN coil 144 of the contactor 142. For hand operation, thebrake 92 is normally energized to braking position, and the brake isreleased when either UP or DOWN button is pushed.

The automatic control system comprises a feed advance relay R-l having acoil and three normally-open contacts, a feed retraction relay R-2having a coil and one normally-closed and one normally-open contact; andan interlock relay R-3 with a coil and two normally-open contacts.

The interlock relay R-3 is closed by the reset button switch 124. Relaycontact R-3a, when closed, energizes the wire leading to the automaticdown-feed controls and holds the relay closed; and its contact R-3b isin series with the manual DOWN coil 144 of the platen motor contactor142; hence this relay must be closed for down feed of the head.

In automatic operation, when automatic feed switch S-l is closed, thisenergizes the coil of relay R-l, which closes a relay hold contact R-1a,and closes contact R-lb in the clutch 102 circuit and contact R-lc inthe solenoid 112 circuit. This causes the rack 106 to move rightward andto drive the feed gear 84. At the end of the rack stroke, the arm 118actuates switch S-3, which opens contacts S-3a in the R-1 holdingcircuit, to open relay R-1 and the clutch 102 and solenoid 112 circuits.Switch S-3 also closes contacts S-3b to energize the coil of relay R-2.This opens contacts R-2a in series with the feed relay R-1 to preventits closure, and closes hold contacts R-2b to hold relay R-2 closedwhile the rack 106 retracts.

During the time the rack is away from its extreme leftward position,switch S-6 will have its contacts S-6a closed, to energize relay R-2,and will have its contacts S-6b open, to reset the timer 132 to zero.When the rack 106 returns to its leftward position it will reverseswitch 5-6, to deenergize the relay R-2 and reclose the timer circuit.

Accordingly, for each closure of the feed switch S-1, the rack 106 willmake one stroke to the right and return, to feed the head down by anincrement fixed by the setting of the stop at the end of the rackstroke.

Also, for each such closure of switch $4, the timer 132 is reset tozero. If the machine fails to feed within the time for which the timeris set, the timer will close switch 134 and thereby stop the operationof the head motor 56.

Limit switch S-2 is in series with the UP coil 143 of the platen motorcontactor 142 and will stop up-travel when it is opened. Limit switchS-4 has contacts respectively in series with the DOWN coil 144 of theplaten motor contactor and with the solenoid 112, so that if switch 54opens it will stop down feed of the feed screw 82 under either manual orautomatic operation. Limit switch S-S has contacts in the controlcircuit for the head motor 56 and in the energizing circuit for theinterlock relay R-3, so that its actuation will stop the head motor andopen relay R-3 to de-energize the automatic feed mechanism and to openthe manual DOWN feed control circuit, and hence will stop down travelunder any circumstances.

The operation of the mechanism described above is as follows. Theworkpiece 66 having a cavity to be lapped is formed to approximate sizeand configuration by other metal-working operations, and it is mountedon the table 12 on blocks 68 by suitable hold-down clamps 70. A lap 64suitable for lapping the cavity of the workpiece 66 is secured in thelap holder 62, and the workpeiece 66 is adjusted into axial alignmentwith the lap 64. Lapping compound is supplied to the lap in accordancewith conventional practice.

The pressure in the cylinder 44 is set to provide a downward force onthe yoke 38 and lap carrier 28 suitable to the size and character of thelap, that is, sufficient to produce lap-cutting downward movement butnot so great as to jam the lap into the cavity and cause galling.

The position of the screw 72 is set to actuate the feed switch 8-1 at adesired point in the lap stroke range, and hence to arrest the downwardcutting stroke of the lap at a selected length of stroke movement, andby this means to control the operating stroke length. For example, witha short lap working on a short cavity, the presssure used will belighter and the stroke shorter than with a long lap in a longer cavity.

The adjustable stop rod 78 is set at a suitable height to terminate thelapping operation when it is completed; and the head is raised orlowered by manual actuation of the feed motor 96 to place the lap 64 ina proper starting position.

The desired feed increment is selected by adjustment of the stop 114 forthe air-driven rack 106.

The lap-reciprocating motor is energized and adjusted by the stroke-ratecontrol 156 to a suitable level. With all such adjustments made, themachine is switched from manual to automatic operation by means of theswitch 128.

At first, until the lap begins its work, the lap strokes will be fullstrokes and on each stroke the feed control switch 8-1 will be closed bythe stroke movement of the screw 72 carried with the yoke, and upon eachsuch closing the incremental feed air cylinder 108 will be actuated onestroke, to feed the head downward by one increment, in the mannerdescribed above. When the lap begins work, the work resistance willprevent the lap from completing its downward strokes until the lappinghas progressed, and when the lap is arrested above the intermediatepoint for which feed actuation is set by the screw 72, the lapreciprocation will continue without feed until the lap has cut its waydeeper into the cavity so that it will again advance to the intermediatepoint at which the feed switch is actuated. An equilibrium condition isthus established during the lap working operation, in which feeding willoccur in accordance with and in response to progress of the lappingoperation into the workpiece cavity.

In this equilibrium state which obtains during the lapping operation,all significant conditions will be regulated in accordance with thesettings of the several adjustments, and the working conditions of thelap will be under precise and selectively variable control, and anydesired combination of conditions may be obtained within a wide range.

We claim as our invention:

1. An automatic lapping machine, comprising a base supporting a worktable for mounting a workpiece,

a head above said table carried by post members guided for perpendicularsliding movement through the plane of the table,

a lap carrier mounted for reciprocation in said head perpendicular tosaid table, lap drive means for reciprocating the carrier throughforward and return strokes of predetermined length,

means to limit the forward-stroke force on the carrier to less thansufficient to overcome a predetermined workpiece resistance whereby suchresistance will arrest forward-stroke movement at an intermediate point,

feed mechanism below said table connected to said post members forraising and lowering said head with respect to said table,

feed drive means which in each actuation thereof drives said feedmechanism to lower said head a predetermined amount,

feed actuating means effecting an actuation of said feed drive means inresponse to each forward-stroke movement of said lap carrier beyond saidintermediate point,

and means to adjust the intermediate point in the maximum stroke lengthat which said feed mechanism is actuated to advance the head, andthereby to vary the operating stroke length under load conditions. 2. Anautomatic lapping machine according to claim 1 in which said lap carrieris biased forward by yieldable biasing means exerting a limited forwardthrust thereon, and

said lap-drive means comprises an eccentric rotor operative to drive thelap carrier through a return stroke against the thrust of said biasingmeans but inoperative to drive the carrier forward, the carrier beingthrust forward by the biasing means, the eccentricity of the rotordetermining the maximum stroke length of carrier reciprocation.

3. An automatic lapping machine according to claim 2, with the additionof means to regulate the force exerted by the biasing means on thecarrier.

4. An automatic lapping machine according to claim 3 with the additionof means to vary the speed of the eccentric rotor thereby to vary thevelocity and stroke-rate of the lap carrier.

5. An automatic lapping machine according to claim 3 with the additionof means to vary the predetermined amount by which each actuation of thefeed drive means lowers the head.

6. An automatic lapping machine according to claim 1, in which said feedmechanism comprises a feed screw element and runner element, one ofwhich is arranged as a lift element to lift said post members and theother of which is a driven element driven by said feed drive means.

7. An automatic lapping machine according to claim 6 in which said liftelement lifts said post members through a lost-motion one-way driveconnection, and means responsive to lost-motion movement of saidconnection for interrupting said feed drive means.

8. An automatic lapping machine according to claim 6, in which said feeddrive means comprises a reciprocable member driven through drive strokesto drive said feed mechamsm,

and means to adjust the increment by which the feed mechanism is drivenduring each such drive stroke.

9. An automatic lapping machine according to claim 1, in which said feeddrive means comprises a reciprocable member and an air pressure devicefor driving the same through a drive stroke for driving said feedmechanism,

means to actuate said air pressure device in response to movement ofsaid lap carrier past said intermediate point,

and adjustable stop means to vary the length of the drive strokes ofsaid reciprocable member and thereby to regulate the increment by whichthe feed mechanism is driven during each drive stroke.

10. An automatic lapping machine according to claim 9, which includes anair valve actuated in response to carrier movement past saidintermediate point, to supply air to drive said air pressure devicethrough a drive stroke,

and reversing means actuated by said reciprocal member to reverse saidair valve for a return stroke of said air pressure device.

References Cited UNITED STATES PATENTS LESTER M. SWINGLE, PrimaryExaminer.

G. WEIDENFELD, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,385,008 May 28, 1968 Richard S. Gentry et a1.

It is certified-that error appears in the above identified patent andthat 'seid Letters Patent are hereby corrected as' shown below:

Column 1, line 34, "3,151,992" should read 3,161,992

Signed and sealed this 18th day of November 1969.

(SEAL) Attest:

WILLIAM E. SCHUYLER, IR.

Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer

